6
$\begingroup$

What happens on the engine after ingesting volcanic ash? Is volcanic ash dangerous for the cockpit crew too? Despite the ground stations, is there any other way to identify volcanic ash while flying?

$\endgroup$
5
  • 4
    $\begingroup$ The British Airways Flight 9 incident will answer pretty much all your questions in real life format en.wikipedia.org/wiki/British_Airways_Flight_9 $\endgroup$
    – Dan
    Dec 2, 2015 at 18:22
  • 1
    $\begingroup$ Or KLM flight 867 $\endgroup$
    – TomMcW
    Dec 2, 2015 at 18:53
  • $\begingroup$ Or this NASA DC-8 $\endgroup$
    – TomMcW
    Dec 2, 2015 at 19:00
  • $\begingroup$ Kinda makes you wonder, between dispatch, the pilots and ATC how can they NOT KNOW a volcano is erupting on their flight path? $\endgroup$
    – TomMcW
    Dec 2, 2015 at 19:02
  • 8
    $\begingroup$ Ash has no radar signature, it must be visually identified and while they may know at the site it may take some time for that information to get to the correct parties and disseminate out. In the air the pilots may see it as heavy cloud cover or simply continued IMC if they are already in IMC. $\endgroup$
    – Dave
    Dec 2, 2015 at 20:09

2 Answers 2

17
$\begingroup$

As mentioned in the comments BA flight 9 is a thorough example of why ash can be a huge issue.

Relevant points of that incident

One issue that ash creates is it cannot be seen on radar so it can be hard to track at night and must be reported by other means. This is deceiving as you would physically see what appears to be a cloud yet weather radar would not show anything.

Inside the cabin, this depends on the granularity of the ash. Some of it will be filtered by the plane's air filters as any particulate matter would. However, ash can be extremely fine and what does make its way through the filters will present itself in a smoke like manner. This may cause alarm in the cabin and a false indication of a fire.

When it comes to the exterior of the plane there are a few issues. The fine grains hitting the plane at that speed will act like sandpaper. The windshield may become scratched to the point you can't see through it (which is not actually as big of an issue as some may assume). The paint will be effectively sanded off which in the short term is not a huge issue. More importantly it could affect your instrument inputs by clogging things like the static ports and pitot tube creating erroneous readings in the cockpit.

The engines were the main issue that arose on BA 9. In short the ash entered the engine, was melted and began to adhere to the blades of the jet. In turn this blocked the engine airflow and caused an engine stall. In the process BA 9 lost all four engines; however, when they began to descend the solidified ash cooled and broke off the engine allowing a restart.

Air crash investigation covered the BA incident nicely in season 4. You can watch it here.

Other risks that BA 9 did not have

For a piston plane ash could potentially clog the air filter and starve the engine of air. Any super-fine ash that could get through the filter runs the risk of being ignited and causing detonation issue with in the engine. Likewise the sanding/grinding issue could have adverse effects on the propeller shape reducing its efficiency or even overall ability to act as an airfoil.

There is a nice wiki on it here and it appears that as of 1991 centers called "Volcanic Ash Advisory Center" have been set up to help track these very issues.

$\endgroup$
3
$\begingroup$

To start, because it's not just ash. Larger particles can be carried in the plume as well. In addition, the intense pressure and temperature of jet engines can reform the debris into larger particles and cause internal damage.

Wikipedia on the 2010 Eyjafjallajökull eruption, which is a likely source of this question.

There is also hazard of external metal and glass damage due to high speed impact with these particles.

Finally, visibility is obviously affected and lightning is a common occurrence in the plumes.

It's bad all around.

$\endgroup$

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .